This invention relates to a vehicle driveshafts, and in particular to a collapsible vehicle driveshaft tube.
Torque transmitting shafts are widely used for transferring rotational power between a source of rotational power and a rotatably driven mechanism. An example of a torque transmitting shaft is a driveshaft tube used in a vehicle driveshaft assembly. The driveshaft assembly transmits rotational power from a source, such as an engine, to a driven component, such as a pair of wheels. A typical vehicle driveshaft assembly includes a hollow cylindrical driveshaft tube having an end fitting secured to each end thereof. Usually, the end fittings are embodied as end yokes which are adapted to cooperate with respective universal joints. For example, a driveshaft assembly of this general type is often used to provide a rotatable driving connection between the output shaft of a vehicle transmission and an input shaft of an axle assembly for rotatably driving the vehicle wheels.
A recent trend in passenger, sport utility and pickup truck vehicle design has been to design and manufacture various components of the vehicle such that they will absorb energy during a front end impact. Each vehicle component in the line of force from a front end impact of the vehicle with another object is designed to absorb a certain percentage of the total energy. By allocating the energy absorption among a number of vehicle components, a more controlled collapse of the vehicle occurs, thereby resulting in increased safety to the occupants of the vehicle.
The vehicle driveshaft assembly is one of the many components which are being used to absorb energy during a front end impact. In the past, driveshaft tubes have been formed having a collapsible design which is adapted to cause the driveshaft tube to collapse when a sufficiently large axial force is applied to the tube. These known collapsible designs include forming a swaged (i.e. a reduced diameter) or a bumped section in the driveshaft tube. Ideally, the force required to collapse the driveshaft tube is designed to be only as large as it needs to be, i.e. large enough to provide a margin of safety above the force values applied to the driveshaft during normal operating conditions. Typically, the axial forces required to collapse the swaged or bumped driveshaft tubes designs have been significantly higher than the desired values. In addition, the swaged tube design results in lower torque carrying capacity due to the reduced diameter of the tube. Ideally, it would be desirable to provide a collapsible driveshaft tube which can provide sufficient torque carrying capacity and which collapses under axial forces which are only as high as needed.